Many different types of pumps exist. One common type is used for pumping fluids from a remote location, such as the bottom of a water well or oil well to a collection location, such as a surface mounted reservoir container. One difficult problem arises because the fluid reservoir in a well may be quite deep in the ground, requiring the pump to produce sufficient energy to lift the fluid from the reservoir to the surface.
One common pump for use in the water and oil well environment is the common pump jack. A frame is mounted at the surface near the well and mounts a pivotal rocker arm. One end of the rocker arm support the sucker rods which extend into the well to the fluid reservoir. Counterweights at the other end of the rocker arm balance the arm. A pumping unit is mounted at the lower end of the sucker rod in the well. A motor is then used to rock the arm about its pivotal axis, causing a reciprocating motion in the pumping unit downhole to lift fluid to the surface. While the pump jack has proven generally satisfactory for many years, it is a massive unit and can often be 2 to 3 stories high. This causes the pump jack to be expensive and difficult to move between wells.
Attempts have been made to improve upon the pump jack for use in the well environment. One such device is disclosed and claimed in U.S. Pat. No. 4,295,799, issued Oct. 20, 1981. This pump uses a sonic pressure wave generated by a surface unit to pump water from within the well. However, one drawback of this pump, as well as many other designs of a similar nature, is the problem of gas locking. In other words, the operation of these pumps relies upon a solid column of liquid extending between the surface unit and the downhole unit. The presence of gas entrained within the fluid decreases the pumping action and, can actually cause the pump to lock or cease functioning. This occurs because the surface unit cannot provide pumping energy to the downhole unit when so much gas is present that the pumping energy produced at the surface is absorbed in the compression and expansion of the gaseous pockets instead of the downhole unit.
A need therefore exist for an improved pumping unit which incorporates the advantages of the prior art in having a surface powered pump while avoiding the prior art disadvantages of complexity, weight, and sensitivity to gas presence within the fluid in the well.